Add downloading message to home screen.

Download files in the background and keep track of progress.

internal/download/Download.go

@@ -30,6 +30,7 @@ func DownloadAudioFiles(progressChan chan<- DownloadStatus, filenames []string,
 	// First, calculate the total size of files that need to be downloaded
 	totalSize := int64(0)
 	filesToDownload := []string{}
+	totalDownloaded := int64(0)
 
 	for _, filename := range filenames {
 		destPath := filepath.Join(destDir, filename)
@@ -62,13 +63,15 @@ func DownloadAudioFiles(progressChan chan<- DownloadStatus, filenames []string,
 
 			// Append it to the list to download
 			filesToDownload = append(filesToDownload, filename)
-			// And increase the total bytes to download
-			totalSize += resp.ContentLength
 		} else if err != nil {
 			logger.Error("unknown error: %v", err)
 		} else {
 			logger.Error("File %s exists, skipping...", filename)
+			totalDownloaded += fileStat.Size()
 		}
+		// Calculate the total of ALL files to give the illusion of
+		// "picking up where you left off" to the user
+		totalSize += resp.ContentLength
 		resp.Body.Close()
 	}
 
@@ -79,8 +82,6 @@ func DownloadAudioFiles(progressChan chan<- DownloadStatus, filenames []string,
 		Msg: "Starting download...",
 	}
 
-	totalDownloaded := int64(0)
-
 	// Download each file that doesn't exist
 	for _, filename := range filesToDownload {
 		url := urlBase + filename